Making an Onan Quiet Generator Quieter!

[avanti]

Originally Posted by hbn7hj

The service manual says frequency is controlled by RPM. It is not an inverter generator.

Well, if we are really talking about the NP30G, the Operator's Manual says the following:

ENGINE GENERATOR
OPERATING SPEED
The generators are driven by single-cylinder engines.
The engines drive revolving fields (rotors), high frequency, permanent magnet alternators. The generators supply 120 volts AC at 60 Hertz. The generators revolving fields are driven at a variable speed depending on the instantaneous demand for power. Computers monitor that demand and adjust the engine speed to provide adequate power to the connected loads.

The mention of "high frequency" from the fields and the statement that speed is load-dependent suggest that it is indeed an inverter generator, no?

http://www.rialtainfo.com/generator/...rac_0661-4.pdf

[Bud]

"The mention of "high frequency" from the fields and the statement that speed is load-dependent suggest that it is indeed an inverter generator, no?

"suggest that it is indeed an inverter generator"

avanti, are you saying that you are not sure?

Bud

[avanti]

Originally Posted by Bud

avanti, are you saying that you are not sure?

Yes, I am saying that I am not sure. I have no first hand data. But the excerpted text is hard to understand if it isn't an inverter generator.

I am also taking at face value the claim that they used the NP30G.

[hbn7hj]

Originally Posted by avanti

Yes, I am saying that I am not sure. I have no first hand data. But the excerpted text is hard to understand if it isn't an inverter generator.

I am also taking at face value the claim that they used the NP30G.

I can't find any brushes in the parts diagram which would mean it is probably an inverter generator. This thing is 20+ years old. Impressive.

When did Honda come out with it's first inverter generator?

[hbn7hj]

Originally Posted by Brad1998RD

Over $3,000.

Yep, a bit rich for a $700 generator with a lot of bad reviews. There were some good reviews.

[Brad1998RD]

It is an inverter generator
"With an inverter generator, the engine is connected to an efficient alternator, which produces AC electricity, just like a conventional generator. But then a rectifier is used to convert the AC power to DC and capacitors are used to smooth it out to a certain degree."

[hbn7hj]

Originally Posted by Brad1998RD

It is an inverter generator
"With an inverter generator, the engine is connected to an efficient alternator, which produces AC electricity, just like a conventional generator. But then a rectifier is used to convert the AC power to DC and capacitors are used to smooth it out to a certain degree."

That is the definition of a converter, not an inverter.

I'll have to dig into the wiring diagram of the generator to try and figure out what is happening. I'm still amazed that there was an inverter generator on the market 20 or more years ago and they didn't advertise it as such.

[Brad1998RD]

No that definition is of an inverter generator just as it's says, directly copied and pasted hence the quotations..
I have a 98 Rialta with this generator. I also went through Winnebago's schooling . The NP30G is a inverter generator.

[JohnnyFry]

I was curious about this generator so I managed to locate a service manual for the device. I have never seen a design like this: it is certainly not what we would normally class as an Inverter generator but it does class as a variable speed generator, within limits. The operating speed range is 2,300rpm to 3,910rpm, a range of 1.7 to. It also mentions the fact that a mysterious device called a "Genistor" divides the high frequency AC output of the alternator to achieve a 60Hz± output. Apparently this unit has a multipole alternator to give a high frequency which is divided down to achieve a nominal 60Hz output. Looking at the schematic there are several windings labeled: Power winding, timing winding, and Power supply winding (there is also a battery charging winding which is not connected to the production of the AC power, except, possibly to provide DC to power the circuitry).

I am guessing here but it appears that the "Genistor" (which appears to be the brains of the operation ) may somehow modulate the field. If the nominal frequency at mid range (3,100rpm) was 2,400Hz we would divide by 40 to get 60Hz output, at the low range of 2,300rpm the output would be 1,780Hz and it w divide by 30 we get 59.5Hz, at the high range of 3,910rpm we get 3,027Hz which we divide by 50 to get 60.5Hz. How this is actually accomplished, whether by somehow modulating the field winding or actually performing the division at the full output voltage (very doubtful as there appear to be no high current devices like IGBTs in the scheme of things).

I would love for others to come in here with other ideas. I will probably waste my time falling asleep trying to work it out.

[hbn7hj]

Thanks, JohnnyFry. I couldn't make sense of it. I saw the various windings and that really confused me.

I knew it wasn't the same as a modern inverter generator. Those have a box in the schematic that says inverter and this didn't have that but it still didn't have any brushes.

"Letting Engine Stabilize"
"The generator supplies correct voltage and frequency only at the proper governed speed" Who knew that was variable.

Their service manual says:
"Computer controlled variable speed RV generator"
I guess that says it all except the how.

"Engine speed is variable and is used to control output voltage and may range from 2520 to 4050."

Frequency is controlled by the Genistor.

As an FYI it doesn't invert anything but the designer deserves a lot of credit. Right up there with Rocket Science!

Wonder how well it worked? Did they all die? Lot of failure points.

[JohnnyFry]

Further reading of the service manual yielded the frequency of the alternator. It is not 1.7K to 3K as I had initially guessed, but actually 336 to 540 Hz.

I wonder what the output waveform looked like, I can't imagine that it was a clean sine wave.

More reading indicates that the field is supplied by a permanent magnet rotor.

[hbn7hj]

Originally Posted by JohnnyFry

I wonder what the output waveform looked like, I can't imagine that it was a clean sine wave.

They show an example of it. Looks like it had some ripple.

[JohnnyFry]

It is an interesting problem: because as the speed changes the divisor must change in steps so the frequency changes to a point where a new divisor is calculated and the frequency jumps for another interval. I would like to watch the waveform as the load and speed changes. I think that the system did not work out to be a practical solution, particularly when true inverter generators came in.

[hbn7hj]

Anyone have one still running? Replacement Genister and CCB boards are probably not available. Electrical repair of this would drive me nuts. The average generator mechanic wouldn't have a clue, either. Thanks again JohnnyFry. The unit deserves a book beyond the service manual.

[JohnnyFry]

If you are interested I'll e-mail a copy of the service manual I found.

[hbn7hj]

Originally Posted by JohnnyFry

If you are interested I'll e-mail a copy of the service manual I found.

I found it, once you said it was there. I was using the Installation and Owners manual.

The designer was certainly a creative guy. Most generators use RPM for frequency and a voltage regulator for voltage. This one uses RPM for voltage and a board full of electronics for frequency.

I suppose the goal was to get away from the 3600 RPM requirement regardless of power output which our Onans still have. It removed the brushes, too.

[JohnnyFry]

Well, of course, now that we have the necessary components readily and cheaply available to build a high powered sine wave inverter there is little need to develop a generator using this type of design. Build a variable speed DC generator, quite possibly using a rare magnet permanent magnet field to reduce complexity, and couple it with a high power sine wave inverter...problem essentially solved...for the most part anyway. Now the problem is to design a reliable small engine and reduce the noise!

[hbn7hj]

I did communicate with the builder of the replacement Rialta generator. He says he has all the business he can handle and sees no problem in starting with a Harbor Freight inverter generator. I do, but that is not my problem.

He also has no interest at this time of replacing the space used by a 2800kw Onan with an inverter generator. Just an FYI.